This invention relates to an apparatus for spinal column fixation. More particularly, but not by way of limitation, this invention relates to a mechanical device used to obtain a rigid posterior spinal column fixation in order to obtain a rigid posterior spinal column bony fusion for disabling back and leg pain.
In one embodiment, the apparatus includes a posterior fixation device which is attached to the involved vertebral bodies. The attachment is made by pedicle screws penetrating into the vertebral body with rigid attachment to ball-and-socket clamps and rods.
The invention also may include a pair of intervertebral metallic or radiolucent wedges inserted into the disc space of the involved vertebrae to increase the stability of the spinal column anteriorly and to avoid breakage of the pedicle screw. Additionally, the application also discloses a method of placing the fixation and wedge device in a posterior lateral approach.
Posterior spinal fusions have been performed on millions of people since at least the early 1900""s. The principle of bony fusion has been and still is stabilization or prevention of motion between two adjacent vertebral bodies.
The most recent attempt to stop motion of the spinal column in order to obtain spinal fusion is internal fixation. One design consist of a series of hooks, rods, screws and wires attached to the lamina or spinous processes to correct deformity or to stabilize the spine.
Another design utilizes screws inserted posteriorly through the pedicle into the vertebral body connecting to plates, rods and clamps to stabilize the two adjacent segments.
The prior art pedicle screw devices have different functions. One function includes the correction of the degenerative curve of the lumbar spine between L3 and S1 or traumatic deformities. These devices have the internal purpose of this device is correction of a deformity through two vertebra such as seen in U.S. Pat. No. 4,987,892 to Martin H. Krag, and in U.S. Pat. No. 5,047,029 to Max Aebi and Robert Mathys, Jr.
Another function includes rigidly fixing the spinal column using a combination of intra-vertebral screws, plates, rods and clamps. In general, see U.S. Pat. Nos. 4,615,681, 4,648,388, 4,655,199 to Steffie; 4,754,326, to Burton; 4,950,269 to Gaines; 4,653,481 to Howland; 4,913,134 to Luque; 4,836,196 to Parke and Weinstein; 4,946,458 to Harms; 5,030,220 to Howland; 4,887,595 to Heinig; and 5,042,982 to Harms.
Another function includes flexible or semi-rigid fixation shown in U.S. Pat. Nos. 4,913,134 to Luque; and, 4,743,260 to Buttem.
The present invention utilizes the rigid posterior fixation device which is attached to the involved vertebral bodies through pedicle screws connected with a series of operably associated ball-and-socket clamps and rods. One such device using a ball connector is seen in U.S. Pat. No. 4,946,458 to Harms. However, the prior art devices include several disadvantages. For instance, many devices were susceptible to breakage, and once breakage occurs, the devices are very difficult to retrieve. Also, the mechanism of clamps and rods is very complicated and difficult for the surgeon to install.
Furthermore, in both the rigid and flexible type of devices, the pedicle screw developed excessive motion and toggle. This in turn would cause the plate to become loose thereby allowing the plate to slide back and forth causing irritation, lack of fixation, and thus failure of fusion.
The rigid devices without inter-body fusion or rigid spacer will result in breakage in the screw because of mechanical factors. The greatest portion of the weight of the individual is taken through the vertebral body and disc. The center of motion of the vertebral segments is located in the posterior aspect of the disc. In the lower lumbar spine the greatest amount of motion is flexion and extension of the trunk, therefore, the intervertebral segment motion is mainly to the anterior frontal or posterior backward movement. Rigid posterior fixation is at a mechanical disadvantage because the forces of weight and motion are anterior to the rigid posterior fixation device. With repetitive motion the device either breaks or becomes loosened. With loosening or breakage, the motion will increase leading to more pain and failure.
Sciatica is pain which shoots down the posterior lateral aspect of the leg. Sciatica is caused by impingement or encroachment on the neural elements in the lumbar spine. Recent studies indicate that intervertebral body fusion is the most effective relief of sciatica. This is because the intervertebral disc is the mechanical center of motion between the intervertebral bodies, and the majority of the body weight of the individual is taken through the vertebral bodies.
Prior art devices are designed and placed in the intervertebral disc comprise several concepts. One is to replace the disc which has been removed with an artificial disc material which can function and behave biomechanically similar to the normal intervertebral disc when inserted in the space.
A second includes maintaining the disc height with no attempt at inter-body fusion. A spacer is placed in after removal of the intervertebral disc.
A third involves maintaining height and obtaining a fusion with a fenestrated spacer that will contain a bone graft. The fenestrated spacer is placed in directly posteriorly under the neural elements.
This invention solves these problem by combining the wedge insert anteriorly and the rigid posterior fixation device allowing the patient to obtain a solid, rigid fixation. The purpose of the wedge is to obtain anterior stabilization, restoration of intervertebral disc height, normal physiological lumbar lordosis, and intervertebral body bony fusion in the human spinal column. The posterior device stabilizes the mechanical dynamics associated with posterior forces, and the wedge compensates the forces associated with the anterior forces.
The invention includes both apparatus and method claims to a spinal column fixation device that includes multiple clamping means for clamping onto an implanted screw in the sacrum and involved vertebrae of a patient. The clamping means will also contain a stabilizing rod and a portion to receive a receptacle stabilizing rod from a complementary clamping means.
In one embodiment, the invention comprises a first sacrum clamping means for clamping to an implanted first sacrum screw in the pedicle of the person""s sacrum, said first sacrum clamping means containing a stabilizing rod. The apparatus will also contain a second sacrum clamping means for clamping to an implanted second sacrum screw in the pedicle of the person""s sacrum, the second sacrum clamping means containing a stabilizing rod.
The invention will contain a first vertebrae clamping means for clamping to an implanted first vertebrae screw in the pedicle of an involved vertebrae, with the first vertebrae clamping means receiving the stabilizing rod of said first sacrum clamping means. A second vertebrae clamping means for clamping to an implanted second vertebrae screw in the pedicle of an involved vertebrae is also provided, with the second vertebrae clamping means receiving the stabilizing rod of the second sacrum clamping means.
In one embodiment, the first vertebrae clamping means further contains a stabilizing rod, and wherein said second vertebrae clamping means contains a stabilizing rod, and the apparatus further comprises a third vertebrae clamping means for clamping to an implanted third vertebrae screw in the pedicle of an involved vertebrae, with the third vertebrae clamping means receiving said stabilizing rods of said third securing means. Also, a fourth vertebrae clamping means for clamping to an implanted fourth vertebrae screw in the pedicle of an involved vertebrae is furnished, with the fourth vertebrae clamping means receiving the stabilizing rods of said second vertebrae clamping means.
In one embodiment, the fourth vertebrae clamping means further contains a stabilizing rod, and the apparatus further comprises a first interconnecting means for interconnecting the stabilizing rod of the fourth and second clamping means. The third vertebrae clamping means contains a receiving portion, and the apparatus further contains a second interconnecting means for interconnecting the stabilizing rod of the first and third clamping means.
The implanted screws contain a first end and a second end, and wherein said first end contains external thread means for threading the implanted screws into the spinal column of the person, and more particularly into the pedicle of the involved vertebra, and sacrum. The second end contains a multi-sided, generally a hexagon, shaped nut member. Further, the hexagon shaped nut member has attached thereto a spherical handle end.
The first, second, third and fourth sacrum, as well as the first, second, and fifth vertebrae clamping means comprises a cap portion having an aperture therein, and wherein the cap portion has a first and second cavity formed therein, the first cavity being formed for receiving the spherical handle ends of the pedicle screws and the second cavity being formed for receiving the stabilizing rods. Also included is a base portion having an aperture therein, and wherein said base portion has a first and second cavity formed therein, the first cavity being formed for receiving the spherical handle ends of the pedicle screws and the second cavity being formed for receiving said stabilizing rod. Next, a bolting member fitted through the aperture of the base and the cap is included and cooperating with the base and the cap so that the spherical handle end and stabilizing rods are adapted to be received within the mating cavities.
The stabilizing rod may extend from the third and fourth sacrum clamping means and has a spherical handle end, and the third vertebrae and fourth vertebrae clamping means will comprise a cap portion having an aperture therein, and wherein the cap portion has a first and second cavity formed therein, the first cavity being to receive said spherical handle end of the pedicle screws and the second cavity being formed for receiving the spherical end of the stabilizing rod, a base portion having an aperture therein, and wherein the base portion has a first and second cavity formed therein, with the first cavity receiving the spherical handle end of the pedicle screws and the second cavity being formed for receiving the spherical end of the stabilizing rod. Also included will be a bolting member fitted through the aperture of the cap and base, and cooperating with said cap and base so that the spherical handle end of the implanted screw and stabilizing rod are adapted to be received within the mating cavities.
In the preferred embodiment, the apparatus may further comprise an intra-vertebral body wedge. The wedge will contain a first end having a tapered end increasing in size; a second end having a tapered end increasing in size; and wherein the first end taper and the second end taper converge at a point which forms the greatest width of the wedge. The wedge member will contain an opening therein for placement of a bone so that a bone graft may be performed. Further, the wedge may contain a threaded aperture for placement of bolting means for placement of an inserter to secure the wedge member for insertion into the discal space in a sagittal plane.
The application also discloses a method of stabilizing motion of involved spinal diseased vertebrae with a spinal fixation device, the spinal fixation device containing a plurality of implanted screws, the implanted screws containing a first and second end, the first end containing thread means and the second end containing a spherical handle end, the spinal fixation device further containing a plurality of spherical clamp means for securing onto the spherical handle ends. The device also contains a plurality of interconnecting rods for interconnecting the ball clamp means. Finally, a wedge member is provided for insertion into inter-discal space.
Generally, the method comprises the steps of performing two posterior lateral incisions or alternatively, one posterior incision on the back of the patient to the area of the involved spinal diseased segments.
Next, the method will expose the transverse process (FIG. 19, 224) of the involved spinal diseased segments; then, dissecting between and lateral to the transverse process of the involved spinal diseased vertebrae is performed so that the nerve roots (FIG. 19, 216) and the annulus fibrosis (FIG. 18, 210) are exposed. Subsequently, a cruciate incision is placed in the annulus fibrosis (FIG. 18, 210) posterior laterally near the intervertebral foramen; then, the surgeon removes the gelatinous disc material and cartilage end plate of the involved spinal diseased vertebrae.
The surgeon then determines the proper size and length of the intra-pedicle screws and the drill point of the drill is placed on the vertebral body at the pedicle starting at the base of the transverse process. A bore hole is then drilled in the pedicle of the involved spinal diseased vertebrae or sacrum for placement of the pedicle screw. The pedicle screw is then rotated into the bored openings of the involved spinal diseased vertebrae with the wrench; and, the surgeon applies a spreader to the pedicle screws so that the disc is opened for placement of the wedge member.
The method may also include the steps of selecting the proper length, height, angle of the wedge member, and then placing a bone in small pieces into the inter-discal space of the involved spinal diseased segments, and in the fenestration of the wedge for intervertebral fusion prior to insertion of the wedge 180. In selecting the proper wedge member, a test wedge may be first employed on a trial basis in order to instre selection of the correct size, length and angle of the wedge.
Following this step, the wedge is inserted (FIGS. 16 and 17A-E) into the inter discal space of the involved spinal diseased vertebrae bilaterally, and the spreader is released which had been keeping the intra-pedicle screws separated thereby allowing the elasticity of the annulus fibrosis and adjacent tissue to lock the wedge in inter-discal space.
Subsequent to this step, the position of the intra-pedicle screws is examined with an image intensifier, and the ball clamp means is placed about the spherical handles of the implanted screws. The fastener member (nut) is tightened so that the ball clamp means will not slip off the spherical handle of the implanted screw. The surgeon will then determine the particular structural arrangement of the interconnecting stabilizing rods.
Next, the cutting of the interconnecting stabilizing rods is performed, with or without spherical balls on the end, to the proper length, and the interconnecting rods are placed into the ball clamp means so that the ball clamp means are linked; and tightening of the ball clamp means is executed so that the ball clamp means encases the spherical handle end and the interconnecting rods. Because of the curved contour of the spinal column, some bending and shaping of the rods may be necessary.
The application also includes a step wherein the process of placing the drill point on the involved spinal diseased vertebral bodies and drilling a bore hole in the ienvolved spinal diseased vertebral bodies includes: placing the drill point on a first and second site of the pedicle of the sacrum; then, placing the drill point on a first and second site of the ala of the sacrum and drilling a bore hole to the first and second site on the ala of the sacrum; then, placing the drill point on a first and second site of the pedicle of the L5 involved spinal diseased vertebral body and drilling a bore hole to the first and second site of the L5 involved spinal diseased vertebral body; and, placing the drill point on a first and second site of the pedicle of the second involved spinal diseased vertebral body and drilling a bore hole to the first and second site of the L4 involved spinal diseased vertebral body.
At this point, completion of the application of the posterior intra-pedicle spinal fixation device is completed. The particular structure arrangement will vary on a case-by-case basis. Thus, the figures of this application show one possible sequence; however, other arrangements will depend on the particular circumstances so that the connections and cross connections can be many different arrangements.
A feature of the present invention includes the ability of using one or two screws on each side of the sacrum. Another feature includes use of triangular cross fixation rods to increase posterior stability. Yet another feature is that when combined with the wedge of the present invention, the device increases stability of the spinal column anteriorly and to avoid breakage of the implanted screws, the wedge creates support in the inter-discal space as well as creating the normal lordosis and increasing stability.
Another feature includes fewer moving parts which allows for the clamps to be mechanically cross connected. Another feature consist of the ball in the socket concept which allows for connecting two clamps at variable angles in both a horizontal and vertical plane, depending on the circumstances of each individual patient. The interconnecting stabilizing rods with a spherical handle end can rotate while in place in the clamping means up and down, as well as laterally relative to the implanted screw.
Still another feature includes the capability of measuring the length of the stabilizing rods during the procedure and cutting the rods to the appropriate length in order to conform to the particular circumstances of the patient. Still yet another feature consist of having less fiddle factor. Another feature consist of having the stem as the weakest point of the implanted screw member which allows for easy removal of the screw if breakage occurs. Put another way, the screw can easily be extracted because the nut and the penetrated portion of the screw is still intact.
An advantage of the present invention includes that the device is easy to insert. Another advantage is that the device allows for adjustable tightness of the various securing means. Yet another advantage includes avoiding breakage of screws.
Another advantage is that multiple clamps connecting to individually associated intra-pedicle screws allows for variations in the number of connecting rods and the variations in the pattern of interconnection. Still another advantage includes that the lamina and the spinous process are not disturbed which leaves a large area for bone grafting. Yet another advantage of the procedure allows for ease of facet joint fusion.
Still another advantage consist of the anterior and the posterior rigid fixation and the large bone grafting area achieved by this invention which leads to solid bony fusion.
Another aspect of the invention involves use of the intervertebral wedge alone for spinal column fixation. The wedge is inserted by expanding the inter-discal space between two vertebrae until a maximum inter-discal space is reached. The implant is inserted between the two vertebrae and is press fit therein. With this press fit, there is no need to use the clamping means and implanted screws described above. To facilitate insertion of the wedge, the facet joint is excised to open the vertebral foramen.
The wedge can include a rounded head to facilitate insertion and serrated side edges to prevent posterior extrusion. The wedge body can be solid for individuals requiring more structural surface for support. The spacers used to press fit the wedges can also have rounded leading edges.